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| #904639 (Received by flhurricane at: 4:49 AM 26.Sep.2017) TCDAT4 Hurricane Lee Discussion Number 33 NWS National Hurricane Center Miami FL AL142017 500 AM AST Tue Sep 26 2017 Lee's cloud pattern has continued to become better organized this evening. The eye has cleared out and has warmed to nearly 10 degrees Celsius, and the eye wall cloud tops have cooled to -63 degrees Celsius. The initial intensity is increased modestly to 85 kt and is based on a blend of the subjective and objective Dvorak T-numbers. It is worth noting that the ADT adjusted raw T-number yields an estimated intensity of 97 kt based on an eye scene-type. The previously noted southeasterly shear undercutting the diffluent flow aloft has certainly diminished and should remain low for the next 48 hours or so. During this initial period, Lee could get a little stronger as indicated in the HWRF hurricane model and the Decay-SHIPS. Afterward, increasing vertical shear, primarily due to the outflow generated by Maria, and decreasing sea surface temperatures should induce a gradual weakening trend as the cyclone moves into a high latitude baroclinic zone and ultimately becomes an extratropical cyclone in 4 days. The intensity forecast is basically an update of 6 hours ago, and follows an average of the IVCN and Florida State Superensemble guidance. The initial motion is estimated to be westward, or 260/9 kt. The cyclone is expected to continue moving within the easterly mid-level steering flow, produced by a relatively narrow mid-tropospheric ridge situated to the north, during the next 24 hours. Afterward, a combination of a broad mid- to upper-level shortwave trough moving out of the eastern Canadian Provinces and a subtropical ridge building east of Lee should steer the hurricane gradually northwestward and northward. On day 3 and beyond, Lee is forecast to accelerate northeastward as it becomes embedded in a deep-layer high latitude southwesterly flow downstream from the aforementioned shortwave trough. Global models and the Cyclone Phase Evolution analysis/forecast product show Lee become a extratropical cyclone no later than day 4. The NHC forecast track is a little south of the previous one through 48 hours, but similar thereafter, and is based on the TVCX and HCCA consensus models. FORECAST POSITIONS AND MAX WINDS INIT 26/0900Z 30.0N 52.5W 85 KT 100 MPH 12H 26/1800Z 29.9N 53.9W 90 KT 105 MPH 24H 27/0600Z 30.2N 55.4W 90 KT 105 MPH 36H 27/1800Z 30.9N 56.4W 90 KT 105 MPH 48H 28/0600Z 32.2N 56.6W 85 KT 100 MPH 72H 29/0600Z 36.9N 53.0W 75 KT 85 MPH 96H 30/0600Z 44.5N 40.2W 60 KT 70 MPH...POST-TROP/EXTRATROP 120H 01/0600Z 50.9N 22.0W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Roberts |
